/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/PolygonFunctions.h
Set the specified vertex of a Simple Polygon. VertexIndex loops around, so e.g., -1 gives the last vertex in the polygon. Does nothing if Polygon has no vertices.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category="GeometryScript|SimplePolygon", Meta=(ScriptMethod)) static void SetPolygonVertex ( [FGeometryScriptSimplePolygon](API\Plugins\GeometryScriptingCore\GeometryScript\FGeometryScriptSimplePolygon) Polygon, int32 VertexIndex, FVector2D Position, bool & bPolygonIsEmpty )